The blog Shapeways did some experiments at home and while finding it a gee-whiz type of science project, was disappointed to see how the results came out when using molds. In particular, the plastic shrunk and deformed to varying degrees.
In the comments section it was suggested that sheets of plastic could be made, allowed to dry (and shrink/deform), and then reheated and shaped as necessary.
The first thing that popped into my mind was using the plastic to craft skulls, masks, and props. It seems like it could be a great help in making a mold that could be used over and over again. Obviously the great benefit is in the relative low cost and ease of access to the ingredients. While the blogs I visited that discussed the process talked a lot about using laser etching and 3-D printers to create stuff, um, I don't have ready access to that. I imagine running this plastic through my inkjet printer won't accomplish much other than making a mess.
Still, it seems worthwhile experimenting with the process and I'll post my results in the future. For now, here's the recipe:
7 parts water
1 part vinegar
1/2 part glycerine (no, that's not the stuff you make dynamite out of)
1-1/2 parts starch
Heat in a pan for several minutes and apparently this creates a thick substance with a glue-like consistency that you can spread out to make sheets. Seems it can take up to a day (or more) to dry and harden depending on the thickness.
According to the Shapeways post, a recipe of 8 parts water, 1 part vinegar, 1 part gycerine, and 1-1/2 parts starch worked best for filling molds and was much easier to work with.
I'm not sure how effective this will ultimately be, but it certainly seems worth trying. I hope some other haunters pick this up who are more technically and scientifically advanced than I am and can improve upon the process.